Control device for dental engines and the like



July 24, 1951 H. M. KECKLEY 2,561,668

CONTROL DEVICE FOR DENTAL ENGINES AND THE LIKE Filed Dec. 28, 1946 3 Sheets-Sheet l 4 n o o 3 7 IO f .I Y fll/l//llll//lQ//ll/ll v2` f (H. JNVENTOR.

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INVENTOR.

3 Sheets-Sheet 2 H. M. KECKLEY CONTROL DEVICE FOR DENTAL ENGINES AND THE LIKE III// y ///I'Il IllI //I/'/ /Qy/// I3 I l I @Nl I July 24, 1951 Filed Dec. 28, 1946 Patented July 24, 1951 CONTROL DEVICE FOR DENTAL ENGINES AND THE LIKE Harold M. Keckley, Dayton, Ohio, assignor, by

direct and mesne assignments, to Wm. 0. Ballard, Toledo, Ohio Application December 28, 1946, Serial No. 718,950

3 Claims.

This invention relates as indicated to a novel control device for dental engines and the like, and more particularly to a foot operated control device adapted to permit considerable freedom of movement on the part of the operator.

It has been conventional to provide foot operated switches for various types of power driven tools such as .dental engines in order that the operator may have both hands free to handle the tool or Work. In the case of dental engines of the type wherein a tool such as a drill is driven by a motor supported on a column adjacent the dental chair, a switch is ordinarily provided on the floor adjacent the base of such chair and the dentist operates the drill by moving the lever of such switch with his foot, the motor stopping when his foot is removed. Such an arrangement, while freeing the dentists hands, has proven very awkward and inconvenient in other ways. To operate such switch it has been necessary for the dentist to stand with all or most of his Weight on one foot, resulting in the development of a very .bad posture, particularly in the tipping of the pelvis, which in time may reach the importance of an occupational disease. Also bad cases of varicose veins often develop in the ankle on which the weight is carried. The dentist must frequently shift his position about the chair and patient while working, and since he must keep his foot upon the switch at all times if the operation of the tool is not to be interrupted, he generally iinds some difficulty in thus moving about the chair, this necessitating frequent movement of location of such foot controlled switch.

It is therefore a primary object of this invention to provide a novel control device for dental engines and the like which will permit a proper and comfortable posture of the operator while operating the same and will facilitate his movement about the chair by eliminating the necessity of shifting the location of the foot control means when he changes position while working on the patient.

Another object of this invention is to provide a oor mat in which means to operate such device is incorporated.

Still another object is to provide mechanism whereby the operator may readily change the speed and direction of rotation of the motor driving the tool.

A further object is to provide a support for the tool so arranged that the motor can not be started while such tool rests on such support.

To the accomplishment of the foregoing' and related ends. said invention. then, consists of the means hereinafter fully .described and particularly pointed out in the claims.

The annexed drawing and the following description set forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the principle of the invention may be used.

In said annexed drawings- Fig. 1 is a general perspective view of a dental chair and dental engine associated therewith showing a preferred arrangement of the new control device;

Fig. 2 is a sectional view through the new floor mat taken along the line 2 2 on Fig. 1;

Fig. 3 is a side elevational view, partly in section, of the control mechanism shown installed in the base of the usual tool supporting column;

Fig. 4 is an end elevational View of such mechanism;

Fig. 5 is a top plan view of such mechanism;

Fig. 6 is a fragmentary detail of the pawl adapted to operate the speed control ratchet;

Fig. 7 is an enlarged detail view of the speed control switch operating means; and

Fig. 8 is a wiring diagram of the various control circuits.

Referring now more particularly to the annexed drawings and especially Figs. 1 and 2 thereof, the control mechanism of the invention is adapted to be installed in the base I of the column 2 which carries the motor 3 adapted to drive the drill or other dental tool 4 through a flexible shaft or endless beit arrangement 5. The tool 4 may be hung when not in use from a hook 6 mounted for slight pivotal movement in a vertical plane on column 2. Incorporated in a molded rubber mat 'I shaped to conform to the base 8 of the dental chair 9 is an elongated tubular member I0 closed at one end and with the other end Il extending beyond such mat. This tubular member is resiliently compressible by foot pressure of the operator whereby fluid pressure may be developed in such extended portion. While such member will ordinarily be oil-lled it may contain other uids such as water, air, etc., if desired.

Referring now to Figs. 3 to 7 inclusive, there is installed in the base I of the column a chamber I2 with which such extension I I of tubular member I0 communicates. A fluid pressure diaphragm I3 in the upper portion of such chamber carries an upwardly directed linger I4. Such nger engages the end portion of element I5 of master switch I6, such element being normally slightly spaced from contact |1 of such switch. When the diaphragm I is moved upwardly under the influence of fluid pressure such element will be caused to engage such contact, thereby closing such switch.

Mounted on the upper surface of the chamber |2 is a frame member i2 supporting a solenoid I5. Journalled in a vertically extending plate member 20 also carried by such chamber is a shaft 2| having a ratchet 22 on that portion extending adjacent solenoid I9. Flanges 22 and 24 depend from frame member il additionally to support such shaft. A pawl 25 is pivotally mounted on the end of an amature 2l supported in a slotted depending tongue 21. A spring 22 attached to the other end of such armature operates normally to hold such pawl out of engagement with the ratchet. A compression spring 25 tends to tilt such pawl outwardly relative to the amature 28 so that such pawl will not engage the teeth of the ratchet should it be moved upwardly through actuation of the amature against the force of spring 22.

A second solenoid 20 is mounted on top of frame member I8 which also carries an armature 3| normally held outwardly from the mechanism through the action of spring 22. The lower end of such armature 2| carries a link 22 pivotally connected to pawl 25. Thus on actuation of solenoid 20, armature 2| will be pulled inwardly causing pawl 25 to be swung into position to engage the teeth of ratchet 22.

Also keyed to shaft 2| to either side of plate 2l are cams 34 and 25 adapted when rotated to operate switches 25, 21 and 28. As shown in Figs. 'l and 8, cam 24 has eight lands and notches and cam 25 has eight lands and notches spaced at different intervals. These cams are keyed to shaft 2| in such relation to each other that upon rota.- tion of such shaft switches 25, 25, and 21 may be sequentially opened and then closed again in reverse order.

The operation of the mechanism may best be understood by reference to Fig. 8 of the drawing. When the dental tool is lifted from its Support 5, such support will be pivoted upwardly under the influence of spring 22 to engage contact 4U. It will thus be seen that the motor 2 cannot be started until such tool has been lifted from its support. Stepping on tube Ill actuates diaphragm I2 to close switch I8, thereby starting the motor. Buch motor is provided with a reversing switch 4| whereby the direction of rotation of the tool may be reversed. As shown diagrammatically in Fig. 8, this switch in reality comprises two single pole double throw reversing switches adapted to be simultaneously operated. It will desirably be set in the mat 1 where it will be within convenient reach of the foot of the operator.

In parallel with such main motor circuit is a circuit including solenoid 22, a resistance 42, and a one-half wave rectifier 43. 'I'he effect of such rectifier is to convert such parallel circuit to direct current. Shunted across such circuit adjacent solenoid 2li is a capacitance 44 which coopcrates with resistance 42 to cause a delay of approximately one-half second in the operation of solenoid 2l.

Thus, when the motor circuit is closed as abovedescribed, solenoid i5 will be activated to move armature 26 with pawl 25 upwardly, but such pawl will not operatively engage ratchet 22 in view of the above-indicated delay in the activation of solenoid 22 which is operative to move pawl 25 into ratchet engaging position. The motor will therefore operate at whatever speed it was operating at when last stopped. The circuits includ- 'ing switches It, 24 and 21 are provided with resistances 45, 45 and 41 respectively bridging the motor circuit in the same manner as main motor resistance 42.

Assuming that cams 24 and 25 have been left in such positions that switches 22, 22 and 21 are all closed, it will be obvious that the motor will be operating at slowest speed. Now, if the operator removes his foot momentarily from tube Il, main switch I6 will be opened, deactivating solenoid Il and permitting armature 2l and pawl 25 to swing away from ratchet 22. Due to the delay in the deactivation of solenoid 22 however, amature 2| will not be at once released, and pawl 2l will remain drawn into ratchet engaging position. If the operator will now again step on tube Il to close switch i5 before solenoid 2l releases armature 2i, the reactivated solenoid Il will cause pawl 25 to turn ratchet 22, thereby opening switch 26. The motor will therefore operate at its next highest speed. This operation maybe repeated, sequentially opening switches 22 and 21 until the motor is operating at its highest speed. Further rotation of ratchet 22 will then sequentially close such switches in reverse order, reducing the speed in the same sequence.A It is obvious that such mechanism provides means whereby the operator has the speed of his motor driven tool under quick control at all times.

It will be seen from the foregoing that there is provided a novel control device for dental engines and the likewhich affords quick and precise control over the operation of such engine while at the same time permitting considerable freedom of movement on the part of the operator. While described in association with a dental engine, it is readily apparent that the control means of the invention is adapted to be employed in conjunction with many types of machine tools where a certain amount of freedom of movement is desirable on the part of the operator and where he requires the use of both hands in handling the work for example. As a further result of the invention, the operator is enabled to stand in a much more comfortable position, is less subject to fatigue, and maintains a better posture.

Other forms may be employed embodying the features of our invention instead of the one here explained, change being made in the form er construction, provided the elements stated by any of the following claims or the equivalent of such stated elements be employed.

I therefore particularly point out and distinctly claim as my invention:

1. Electric motor speed change means comprising a resistance shunted across such motor circuit, a. switch operative to open and close such shunt circuit, a ratchet, a pawl operative to drive said ratchet, a solenoid operative to move said pawl to turn said ratchet, a spring adapted to hold said pawl out of ratchet-engaging position, a second solenoid operative to move said pawl against the force of said spring into ratchetengaging position, delay means associated with said second solenoid operative in delay energizetion of said second solenoid until after said firstnamed solenoid has been energized and to continue energization of said second solenoid for a designated time interval after de-energization of said first-named solenoid, whereby said pawl will be able operatively to engage said ratchet upon first energizing said solenoids but will operatively engage said ratchet upon re-energization of said solenoids within such time interval, and means actuated by rotation of said ratchet operative to open and close said switch.

2. Electric motor speed change means comprising a plurality of resistances shunted in parallel across such motor circuit, a switch for each such shunt circuit operative to open and close such shunt circuits individually, a ratchet, a pawl operative to drive said ratchet, a solenoid operative to move said pawl to turn said ratchet, a spring adapted to hold said pawl out of ratchetengaging position, a second solenoid operative to move said pawl against the force of said spring into ratchet-engaging position, delay means associated with said second solenoidv operative to delay energization of said second solenoid until after said first-named solenoid has been energized and to continue energization of said second solenoid for a designated time interval after deenergization of said rst-named solenoid, whereby said pawl will be unable to operatively engage said ratchet upon ilrst energizing said solenoids but will operatively engage said ratchet upon re-energization of said solenoids Within auch time interval, and cam means actuated by said ratchet operative to open and close said switches in desired sequence.

3. Electric motor speed change means comprising a resistance shunted across such motor circuit, a switch operative to open and close such shunt circuit, a ratchet, a pawl operative to drive said ratchet, means adapted to move said pawl to drive said ratchet, means operative to keep said pawl from operatively engaging said ratchet when thus moved, means operative to overcome said last-named means and move said pawl into ratchet-engaging position, delay means operative upon energization of the circuit including said pawl operating and control means to delay operation of said means operative to move said pawl into ratchet-engaging position and upon de-energization of such circuit to continue to hold said pawl in ratchet engaging position for a designated time interval, whereby said pawl will be unable operatively' to engage said ratchet upon rst energizing such circuit but will operatively engage said ratchet upon re-energization oi.' such circuit within such time interval, and means actuated by rotation of said ratchet operative to open and close s'aid switch.

lHAROLD M. KECKLEY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Bressler July 30, 1940 

